1. Field of the Invention
The present invention generally relates to a touchable control system, and more particularly to a power management device of a touchable control system for rapidly replying to a sleep mode.
2. Description of Related Art
A touch panel may be combined with a display screen to result in a touch screen. Touch screens have been widely used as input interfaces for electronic devices for detecting touch inputs within a display area. If no touch inputs input to the touch screen, users usually close the power supplied to the touch screen to enable the sleep mode for avoiding the unnecessary power consumption.
FIG. 1A shows a schematic circuit of a power management device 1 of a conventional touchable control system. As mentioned above, if the power of the touch screen is closed to enable the sleep mode, there are neither input signals of VDD and CK/CKB, nor output voltage Vout and the loading circuit is disabled, wherein VDD is a logic high-level voltage (or the low voltage) of a pulse/inverted-pulse signal CK/CKB.
FIG. 1B shows an operating state of the power management device 1 of the conventional touchable control system. If the users need to use the touch panel to restore the sleep mode to the operating mode, the loading circuit has to reach the operating voltage VDDH. In view of FIG. 1A, the loading circuit electrically connects to the output terminal 11t of the boost circuit 11 so as to consume the output current IO. That is, the consumption adds the loading current ILoad. The output voltage Vout usually utilities an external capacitor Cext to charge as the operating voltage of the loading circuit. In other words, if the touchable control system restores the sleep mode to the operating mode, the external capacitor Cext will start to charge. However, the output current IO do not fully flow to the external capacitor Cext but the loading circuit consumes a part of the output current Io, wherein the consuming output current IO is the loading current ILoad. Therefore, it takes much charge time to make the external capacitor Cext reach the operating voltage VDDH of the loading circuit, as shown in the curve 1.
As mentioned above, the loading circuit of the touchable control system needs to reach a predetermined operating voltage so as to restore the operating mode. However, the conventional designed touchable control system will charge the external capacitor to the operating voltage while receiving touch inputs. Although the charge time may be only few microseconds, which still make the users feel slow or delay with the conventional touchable control system.
A need has thus arisen to propose a novel power management device for rapidly replying to the sleep mode of the conventional touchable control system.